YB1680
1.5MHz, 600mA Synchronous Step-Down Converter
Function Block
Figure 3: Function Block
Operation
YB1680 is a monolithic switching mode
Step-Down DC-DC converter. It utilizes
internal MOSFETs to achieve high
efficiency and can generate very low output
voltage by using internal reference at 0.6V.
It operates at a fixed switching frequency,
and uses the slope compensated current
mode architecture. This Step-Down DC-DC
Converter supplies 600mA output current at
V
IN
= 3V with input voltage range from 2.5V
to 5.5V.
Current Mode PWM Control
Slope compensated current mode PWM
control provides stable switching and
cycle-by-cycle current limit for excellent
load and line responses and protection of
YB1680 Rev.1.0
the internal main switch (P-Ch MOSFET)
and synchronous rectifier (N-CH MOSFET).
During normal operation, the internal P-Ch
MOSFET is turned on for a certain time to
ramp the inductor current at each rising
edge of the internal oscillator, and switched
off when the peak inductor current is above
the error voltage. The current comparator,
I
COMP
, limits the peak inductor current.
When the main switch is off, the
synchronous rectifier will be turned on
immediately and stay on until either the
inductor current starts to reverse, as
indicated
by
the
current
reversal
comparator, I
ZERO
, or the beginning of the
next clock cycle. The OVDET comparator
controls output transient overshoots by
7
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